Study on Mechanisms for Progression and Regression of Diabetic Glomerular Injury and Role of Novel Humoral Factors

为了探讨糖尿病肾小球损伤进展和消退的机制以及新的体液因子在这一过程中的作用，我们利用基因工程小鼠模型，研究了细胞外基质相关分泌蛋白、脂肪组织衍生激素瘦素和心脏激素利钠肽等CCN家族(CCN1、CCN2)在体内的作用。结缔组织生长因子(CCN1)是一种介导转化生长因子-β纤维化特性的促纤维化蛋白，在糖尿病肾病中正常表达并上调。我们建立了足细胞特异性CTGF转基因(TG)小鼠，并检测了CTGF在糖尿病环境中的过表达。在链脲佐菌素(STZ)诱导的糖尿病肾病过程中，CTGF-TG小鼠在基础状态下没有表现出任何异常，但与野生型小鼠相比，蛋白尿显著增加(~3倍)。结缔组织生长因子-TG小鼠…肾小球系膜扩张更明显，足细胞数量减少、空泡化，提示足细胞损伤加重。相比之下，CCN2(富含半胱氨酸的蛋白61，Cyr61)，另一种足细胞来源的体液因子，被认为具有肾脏保护作用。在含有neparin启动子的足细胞特异性Cyr61-TG小鼠中，与野生型小鼠相比，STZ诱导的糖尿病期间肾小球肥大不那么明显。然后，我们研究了脂肪萎缩性糖尿病模型A-ZIP/F-1小鼠的肾脏异常。该小鼠模型表现为进行性肾病范围蛋白尿、显著的肾小球肥大伴系膜扩张、肾小球基底膜增厚，这些都是晚期人类糖尿病肾病的特征。瘦素基因的转基因过表达或瘦素的药理作用进入这个模型几乎完全正常了这些异常的表型。最后，在BNP-TG小鼠中，长期过量生产脑利钠肽在蛋白尿、系膜扩张和系膜上调ERK/转化生长因子-β级联反应方面显著抵抗糖尿病肾小球损伤。这些发现提示瘦素和利钠肽在糖尿病肾病中的治疗潜力。较少

In order to explore the mechanisms for progression and regression of diabetic glomerular injury and to investigate the roles of novel humoral factors in such processes, we examined the in vivo effects of the CCN family (CCN1, CCN2) that are extracellular matrix-associated secretory proteins, fat tissue-derived hormone leptin, and cardiac hormone natriuretic peptides, using genetically engineered mouse models.CCN1 (connective tissue growth factor, CTGF), a profibrotic protein mediating fibrogenic properties of TGF-β, is expressed normally in glomerular podocytes and upregulated in diabetic nephropathy. We established the podocyte-specific CTGF-transgenic (Tg) mice using human nephrin promoter, and examined effects of CTGF overexpression in the diabetic milieu. CTGF-Tg mice did not show any abnormality at basal state, but exhibited significantly enhanced proteinuria (〜3-fold) compared with wild-type mice during the course of streptozotocin (STZ)-induced diabetic nephropathy. CTGF-Tg mice … More also showed more pronounced mesangial expansion, with decreased number and vacuolar changes of podocytes, indicating aggravation of podocyte injury. In contrast, CCN2 (cysteine-rich protein 61, Cyr61), another podocyte-derived humoral factor, is suggested to have renoprotective properties. In podocyte-specific Cyr61-Tg mice with the nephrin promoter, glomerular hypertrophy was less prominent during STZ-induced diabetes as compared with wild-type mice.We then investigated renal abnormalities in A-ZIP/F-1 mice, a lipoatrophic diabetes model. This mouse model revealed markedly progressive nephrotic-range proteinuria, remarkable glomerular hypertrophy with mesangial expansion, and glomerular basement membrane thickening, which are characteristics of human diabetic nephropathy at advanced stages. Transgenic overexpression of the leptin gene or pharmacological administration of leptin into this model almost completely normalized such abnormal phenotypes. Finally, chronic overproduction of brain natriuretic peptide (BNP) in BNP-Tg mice was significantly resistant against diabetic glomerular injury in terms of proteinuria, mesangial expansion, and mesangial upregulation of the ERK/TGF-β cascade. These findings suggest the therapeutic potential of leptin and natriuretic peptides in diabetic nephropathy. Less